Using the white carneau pigeon as an animal model for human arteriosclerosis, we are studying the relationship of natrally occurring atherosclerosis to deafness as well as the relationship of atherosclerosis aggravated with a high cholesterol diet to deafness. Our high cholesterol diet animals are being studied under a one year period of progression on the diet, followed by a one year period of regression. The function of the inner ear sensory cells is being measured by round window A.C. cochlear potentials, and the histopathology of the inner ears of our animals are being looked at with light microscopy, transmission electron microscopy, scanning electron microscopy, and special chemical stains with frozen section material. Concurrent studies of hematology and blood coagulation have demonstrated that the loss of inner ear electric potentials occurs with chronic hypercoagulation. Concurrent measurements of blood pressure indicate that at a very young age the inner ear is not affected by the range of blood pressure in the animal model. If anything there is a tendency for the young animals with high normal blood pressure to have better inner ear function electrically than those with lower blood pressure. In middle age animals there is no blood pressure effect at all on the inner ear; however, in the older animals there is a very significant correlation between hypertension and the loss of inner ear A.C. cochlear potentials.